What would be more helpful to become a more articulate speaker joining a Toastmaster club or using that time to write?

I would suggest you are posing an apples vs oranges style of question.

Speaking and writing are two very different activities. Yet to be effective in either activity, you need to be skilled in both.

The Toastmasters program will provide you with ample opportunity to speak. As you participate in their new Pathways Program you will be provided with projects that allow you to research and write speeches you will then deliver orally.

Articulation comes with experience. The more you speak publicly and receive constructive feedback as you would in a Toastmasters meeting, the quicker you will become articulate.

Writing for a speech is different than writing a book. Whereas, when writing content to be read, you can add punctuation to help the reader understand how the sentence should be read. E.g. question marks to indicate a question is being asked or exclamation mark to indicate surprize or importance. Sentences can be longer. As a reader, we can go back and reread a sentence if we want to understand it better.

Written content for a speech is different. The sentences need to be short. The listener is unable to listen to a sentence again if it is a live presentation. The speaker’s voice needs to help the listener understand the message as there is no punctuation to view. This is where vocal variety comes in. Speaking faster. Speaking slower. Speaking louder. Speaking softly.

I’m an anomaly in that I have given hundreds of speeches but have only written a few of them before delivering the speech.

On the other hand, I’ve written a dozen or so books in the self-help genre. My style of writing is conversational, albeit one-sided. Now I’m narrating my books aloud for on-line e-courses and will try recording one of my books as an audio version.

I would suggest you join Toastmasters to increase your articulation. Continue to write whenever you have the time. Topics to speak and write about are unlimited. Stretch your imagination.

Toastmasters is a self-directed program, meaning you progress and participate at your own speed. Doing both activities would not be onerous.